Abstract:

BaTiO₃ has a wide range of applications in microelectromechanical systems and integrated circuits due to its excellent dielectric, ferroelectric, piezoelectric, and pyroelectric properties. For the applied research and device applications of BaTiO₃ films, reducing its deposition temperature to be compatible with the CMOS-Si technology is an important Challenge. Here, with the help of a LaNiO₃ buffer layer which has a closely-matched lattice with BaTiO₃, (001)-textured BaTiO₃ films were sputter-deposited at 450 ℃ on single crystalline Si(100) substrates, which consisting of well-cryotallized, evenly-distributed columnar nanograins with an average grain size of 27 nm. Our result showed that this deposition temperature can maintain the columnar nanograin structure with a relatively large grain size, leading to a good ferroelectric performance. In addition, a small residual strain on Si was also helpful to improve its ferroelectric and dielectric properties. The remnant polarization and saturated polarization of these BaTiO₃ films reached 7 and 43 μC·cm^-2, respectively, while leakage current densities were as low as 10^-5 A·cm^-2 at an applied electric field of 0.8 MV·cm^-1. These BaTiO₃ films also displayed excellent frequency stability with a low dielectric loss in which relative dielectric constant measured to be ~155 at 1 kHz, slightly being reduced to ~145 after increasing the frequency to 1 MHz. Meanwhile, the dielectric loss slightly increased from 0.01 at 1 kHz to 0.03 at 1 MHz. Lastly, through capacitance-voltage (C-V) tests, these films exhibited a large dielectric tunability of~51% and a figure of merit (FOM) of ~17 (@1 MHz). These films have a good potential for applications in tunable dielectrics.

Key words: silicon, BaTiO₃, ferroelectric film, columnar nanograins, dielectric tunability, figure of merit